Genetic mapping of new DNA probes at Xq27 defines a strategy for DNA studies in the fragile X syndrome

G. K. Suthers, J. C. Mulley, M. A. Voelckel, N. Dahl, M. L. Väisänen, P. Steinbach, I. A. Glass, C. E. Schwartz, B. A. Van Oost, S. N. Thibodeau, N. E. Haites, B. A. Oostra, R. Giné, M. Carballo, C. P. Morris, J. J. Hopwood, G. R. Sutherland

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


The fragile X syndrome is the most common cause of familial mental retardation and is characterized by a fragile site at the end of the long arm of the X chromosome. The unusual genetics and cytogenetics of this X-linked condition make genetic counseling difficult. DNA studies were of limited value in genetic counseling, because the nearest polymorphic DNA loci had recombination fractions of 12% or more with the fragile X mutation, FRAXA. Five polymorphic loci have recently been described in this region of the X chromosome. The positions of these loci in relation to FRAXA were defined in a genetic linkage study of 112 affected families. The five loci - DXS369, DXS297, DXS296, IDS, and DXS304 - had recombination fractions of 4% or less with FRAXA. The closest locus, DXS296, was distal to FRAXA and had a recombination fraction of 2%. The polymorphisms at these loci can be detected in DNA enzymatically digested with a limited number of restriction endonucleases. A strategy for DNA studies which is based on three restriction endonucleases and on five probes will detect one or more of these polymorphisms in 94% of women. This strategy greatly increases the utility of DNA studies in providing genetic advice to families with the fragile X syndrome.

Original languageEnglish (US)
Pages (from-to)460-467
Number of pages8
JournalAmerican journal of human genetics
Issue number3
StatePublished - Mar 1991

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)


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